Gregor said:
Interesting idea to use the bending of the clamp for holddown.
Might be easier to put another domino hole horizontally through each side block (or the bottom somewhere between the side blocks) so you can use the clamp normally, should give higher / more even pressure and be easier to clamp.
Not sure why an extra horizontal hole would make it easier to clamp. The clamp pulls the 2 wedges together. With more pressure the wedge comes closer to each other and their base move further away, thus giving the pressure needing on the workpiece. Additional wedges might be installed under the horzontal bar in order to get downward pressure (keeping the pieces flat). Maybe the horizontal bar should be a T shape...